1. Technical Field
The present invention relates to a technique for making deterioration in display quality occurring at the time of sampling a phase-developed data signal invisible.
2. Related Art
Recently, projectors forming a compact and reduced image using a display panel such as a liquid crystal panel and enlarging and projecting the compact and reduced image using an optical system have been widely adopted. Since such projectors do not have a function of creating an image themselves, the projectors are supplied with image data (or image signals) from an upper level apparatus such as a PC or a TV tuner. Since the image data serve to specify a grayscale level (brightness) of pixels and are supplied in such a manner of horizontally and vertically scanning pixels arranged in a matrix, it is desirable to drive display panels used in projectors in the same manner. Therefore, it has been common practice to drive the display panels used in a projector using a dot sequential method in which scan lines are selected in a predetermined order, data lines are sequentially selected in a time period when one scan line is selected, and the selected data line is supplied with data signals which are converted from the image data so as to be suitable for driving liquid crystal.
Meanwhile, there have been efforts for realizing a higher definition of display images such as high vision. The higher definition of the display images may be realized by increasing the number of scan lines and the number of data lines. However, since a frame frequency is fixed, an increase in the number of scan lines may shorten one horizontal scanning period and an increase in the number of data lines may shorten a period for selecting the data lines in the dot sequential method. Therefore, in the dot sequential method, when attempting to achieve higher definition, it may not be possible to secure a sufficient time for supplying the data signals to the data lines, thereby making the writing of data to the pixels insufficient.
In order to solve the insufficient writing of data, a phase-developed driving method has been suggested in JP-A 2000-112437. The phase-developed driving method is a method in which every predetermined number, for example, three, of data lines are grouped together (for example, every six data lines are grouped in JP-A-2000-112437), and the data lines of each group are selected in a predetermined order in one horizontal scanning period, and the selected data lines are supplied with data signals, the time required to perform this operation being increased in accordance with the number of scanning lines in each group. In the phase-developed driving method, since the time for supplying the data signals to the data lines is proportionally increased, for example by three times, compared with the dot sequential method, the phase-developed driving method is considered to be suitable for higher-definition display.
However, in the phase-developed driving method, a vertical stripe pattern in which the grayscale level of pixels is slightly changed in units of the grouped data lines selected at the same time may be produced. Therefore, deterioration of display quality becomes conspicuous in the phase-developed driving method.